C语言socket判断网络是否联通(支持域名/附源码)

有时候需要用代码判断当前网络是否联通

#include <stdio.h>#include <sys/socket.h>#include <netinet/in.h>#include    <net/if.h>#include <string.h>#include <stdlib.h>#include <stdio.h>#include <signal.h>#include <arpa/inet.h>#include <sys/types.h>#include <sys/socket.h>#include <unistd.h>#include <netinet/in.h>#include <netinet/ip.h>#include <netinet/ip_icmp.h>#include <netdb.h>#include <setjmp.h>#include <errno.h>

//#define NET_PORT 53//#define NET_IP "8.8.8.8" //谷歌DNS#define NET_PORT 80#define NET_IP "www.baidu.com" //百度80端口

//获取联网状态int check_net(void){    int fd;    int in_len=0;    struct sockaddr_in servaddr;    struct hostent *host;    unsigned int inaddr=0l;    struct in_addr *ipaddr;    in_len = sizeof(struct sockaddr_in);    fd = socket(AF_INET,SOCK_STREAM,0);    if(fd < 0)    {        perror("socket");        return -1;    }    /*设置默认服务器的信息*/    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons(NET_PORT);    //servaddr.sin_addr.s_addr = inet_addr(NET_IP);    memset(servaddr.sin_zero,0,sizeof(servaddr.sin_zero));    /*判断是主机名还是ip地址*/    if( inaddr=inet_addr(NET_IP)==INADDR_NONE)    {        if((host=gethostbyname(NET_IP) )==NULL) /*是主机名*/        {            perror("gethostbyname error");            return (-1);        }#ifdef DEBUG        printf("0IP Address : %s\n",inet_ntoa(*((struct in_addr *)host->h_addr)));        printf("1IP Address : %s\n",inet_ntoa(*((struct in_addr *)host->h_addr_list[1])));        printf("h_name : %s\n",host->h_name);        printf("h_aliases : %s\n",host->h_aliases);        printf("h_addrtype,h_length : %d,%d,AF_INET=%d\n",host->h_addrtype,host->h_length,AF_INET);#endif//方法1：        ipaddr = (struct in_addr *)host->h_addr;servaddr.sin_addr.s_addr = (ipaddr->s_addr);//方法2：这个算是多此一举了！多了一句无用功//      inaddr = inet_addr(inet_ntoa(*ipaddr));//servaddr.sin_addr.s_addr = inaddr;}    else    /*是ip地址*/    {        servaddr.sin_addr.s_addr = inaddr;    }    /*connect 函数*/    if(connect(fd,(struct sockaddr* )&servaddr,in_len) < 0 )    {        printf("not connect to internet!\n ");        close(fd);        return 0; //没有联网成功    }    else    {        printf("=====connect ok!=====\n");        close(fd);        return 1;    }}

上述函数可能有待于优化，因为如果短时间内连续执行可能会出现停滞的情况，打印不出来connet ok！不过1s调用一次这个函数来检测应该是可以的！

欢迎网友为我指正里面的不足之处！